LEC 2 Biology (7) - Mashreq University PDF

‫بسم هللا الرحمن الرحيم‬ The Structure of Microscope disteducation.mashreq.edu.sd/  Types of Microscopes ▶ Light microscopes(L/M) ▶ Electron microscopes (E/M)  Transmission electron microscopes  Scanning electron microscopes ▶ Fluorescence microscopes ▶ Super...

‫بسم هللا الرحمن الرحيم‬ The Structure of Microscope disteducation.mashreq.edu.sd/  Types of Microscopes ▶ Light microscopes(L/M) ▶ Electron microscopes (E/M)  Transmission electron microscopes  Scanning electron microscopes ▶ Fluorescence microscopes ▶ Super resolution microscopes ▶ X-ray microscopes ▶ The Atomic Force microscopes ▶ The phase- Contrast Microscope There are two types of light microscope: I- Simple Microscope: Uses a single lens. II- Compound Microscope: Uses two lenses. Simple Light microscope Compound light microscope ▶ In a compound light microscope: Light rays passing through a specimen are brought to a focus by a set of glass lenses, and the resulting image then viewed by the human eye. ▶ In the transmission electron microscope: Electrons passing through a specimen are brought to a focus by a set of magnetic lenses, the resulting image is projected onto a fluorescent screen or photographic film. ▶ A scanning electron microscope: Provides a three-dimensional view of the surface of an object. Fluorescence Microscope ▶ As microscopic techniques: developed, to use of various histochemical, immunocytochemical, and staining techniques. ▶ The light source for the early microscopes was sunlight. In modern microscopes, an electric light bulb with tungsten filaments serves as the main light source. ▶ The simplest light microscopes, examination of mammalian cells showed a nucleus and a cytoplasm, surrounded by cell membrane. ▶ a microscope to see most cells and lower levels of biological organization (Cells are visible with the light microscope, but not in much detail). ▶ An electron microscope is needed to see organelles in detail and to make out viruses and molecules. The sizes of living things and their components.  Compound Microscope  All optical microscopes share the same basic components: The ocular or eyepiece : To bring the image into focus for the eye, The eyepiece is inserted into the top end of the body tube. Eyepieces are interchangeable and many different eyepieces can be inserted with different degrees of magnification. Typical magnification values for eyepieces include 5x, 10x and 2x. Some eyepieces have a pointer. The objectives lenses : - A cylinder containing one or more lenses, typically made of glass, to collect light from the sample. - At the lower end of the microscope tube one or more objective lenses are screwed into a circular revolving nosepiece which may be rotated to select the required objective lens. - Typical magnification values of objective lenses are 4x, 5x, 10x, 20x, 40x, 50x and 100x. objective lenses: 4x: low power 10x: mid power 40x, high power 100x: oil immersion, when used it should be immersed in a drop of cedar oil, that to be examined How we can calculated the magnification of sample or objects? The stage : A plat form below the objective which supports the specimen being viewed. In the center of the stage is a hole: through which light passes to illuminate the specimen. The stage usually has arms to hold slides (rectangular glass plates with typical dimensions of 25 mm by 75 mm, on which the specimen is mounted). The mechanical stage: with a control knob The illumination source: below the stage, light is provided and controlled in a variety of ways. At its simplest, daylight is directed via a mirror. controllable light source : That is focused through an optical device which concentrates it called a condenser diaphragms: Controlling the amount of light let through and filters available to manage the quality and intensity of the light. a rigid arm : which is attached to a base Adjust coarse focus: move the stage up or down to focus the object, with a smaller one to control 'fine focus’ 1.The ocular or eyepiece 2.Rotated disc 3. The objectives lenses 4. Adjust coarse 5. Fine focus 6. The stage 7. light source 8. condenser 9. Mechanical stage 10. The rigid arm 11. a control knob 12. a base 13. Diaphragms  The Metric System In science we use the metric system for measuring. Here are some measurements and conversions that will aid your understanding of biology. 1 meter = 100 cm = 1,000 mm = 1,000,000 μm = 1,000,000,000 nm 1 centimeter (cm) = 1/100 meter = 10 mm 1 millimeter (mm) = 1/1000 meter = 1/10 cm 1 micrometer (μm) = 1/1,000,000 meter = 1/10,000 cm 1 nanometer (nm) = 1/1,000,000,000 meter = 1/10,000,000 cm Thank You